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Has anyone else noticed a sudden lack of reading comprehension skills?
(sh.itjust.works)
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this post was submitted on 22 Aug 2023
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I don't really think this is showing what you think it is - table 4 references four studies which finds a significant difference in volume of the prefrontal lobe... but table 3 references three studies which do not find a significant difference. The sample sizes are very low in almost all of the studies being fewer than 20 people with ADHD. And even those studies which show that statistically significant difference have a relatively high probability that the results are explained by chance (heterogenity p)
There's quite a bit of research into this area, but it has all of the classic problems of ADHD studies, having been conducted on predominantly male children. Studies have been conducted on adults with ADHD and tend to find a significantly smaller difference, if any. A lot of the studies I read about stated explicitly that any difference, when compensated for gender, age, race, etc. is so slight as to be completely unnoticeable unless the imaging was conducted by expert specialists who were specifically looking for it.
Table 3 and Table 4 aren't combined because they assessed different regions of interest. The tables don't contradict each other, because they don't even include the same ROIs:
As for the heterogeneity, the paper notes which ROIs failed to remain statistically significant after correction. The Prefrontal region is not included this list:
As you say, the studies aren't golden, but that's why I picked a meta-analysis. To be honest, if I knew I was going to be held to such a high standard, I would have just kept my mouth shut!
I don’t think that’s quite right - I no longer have the study in front of me to reference and I may have misread it, but if I remember correctly, the definition of Table 3 is the findings of studies that DO NOT show significant SMDs and Table 4 is studies that DO. If you look at the descriptions of table 3 and table 4 and compare then I think you’ll see what I mean. It may even be in the titles of the tables, I’ll check it again when I get home in case I misread, in which case I apologise.
And yeah, the authors call out the high probability of chance for those regions especially, but that doesn’t mean the other regions are perfect either - the data is all there in table 4, you can look for yourself! It’s the heterogeneity columns, the lower the p value, the more likely the effect is consistent. A p value of 0.05 is usually considered the baseline for statistical significance, or for meta analyses with low sample sizes (such as this one), it’s not unreasonable to consider higher values significant because of differences in methodology, but these are some pretty high values.
I’m not saying that any of this is reason enough to fully discount the findings, or that there’s no correlation found by the studies, it’s just that, in my personal opinion, the quantity of the data is significantly too low, too narrow in scope, and the margin of error is too large to use the data to say “yes, we can identify differences in brain volume between an average person with ADHD, and an average person without ADHD” with any confidence.
At best, you could say that “given an average white male child with ADHD, there’s a higher than normal chance that the prefrontal regions of their brain would be lower than average” and even that is quite an opinionated stance tbh
I’m sorry for making you feel attacked though, you seem to have made the claim in good faith, it’s just that a lot of people make claims like that in poor faith and use it to justify treating people with neurological differences as inferior people or even as subhuman, so I think it’s important that people don’t make broad statements about how science has proven that people with ADHD have smaller brains or whatever.